GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 3.2 GNGTS 2024 The Italian calibraton and reference site for E & EM geophysical methods: The HydroGeosITe A. Signora 1 , S. Galli 1 , F. Daut 1 , A. L. Sullivan 1 , A. Lucchelli 1 , M. Gisolo 2 , G. Fiandaca 1 1 The EEM Team for Hydro & eXploraton, Department Of Earth Sciences “Ardito Desio”, Università degli Studi di Milano, Milano (Italy) 2 A2A Ciclo Idrico S.p.a. , Brescia (Italy) 1. The HydroGeosITe project From the spring of 2021 to July 2023 over 20000 line-km of airborne electromagnetc (AEM) data have been acquired for mapping and managing groundwater resources in the entre plain of Brescia province and a mountainous sector, over an area of approximately 1800 km 2 (Figure 1). Within this AEM campaign, the largest ever carried out in Italy for groundwater mapping and management, the water management company A2A Ciclo Idrico S.p.A. fnanced the HydroGeosITe project, which aims at establishing the frst calibraton and reference site for galvanic methods and for ground and airborne electromagnetc methods, for hydrogeological purposes. The need for calibraton sites of EM systems derives by the sensitvity of EM data to system characteristcs, such as receiver transfer functon, transmiter current waveform, and transmiter-receiver synchronizaton and geometry, which if neglected lead to signifcant bias in the retrieval of the electrical propertes (Christansen et al., 2011). For instance, the Lyngby Danish reference site has been established for ensuring the calibraton of both airborne and ground-based EM systems (Foged et al., 2013), while the Menindee Australian test range (Brodie and Cooper, 2018) focuses only on airborne systems, but covers a much longer stretch (more than 35 km). In both cases, calibrated systems are expected to retrieve satsfactory resistvity models, the eventual calibraton consistng in adjustng the system characteristcs untl the inversion model compares well enough with the reference model. Within the HydroGeosITe we have characterized the electrical propertes of the subsurface with an unprecedented density of measurements, both in terms of conducton and polarizaton. This efort aims also to test a new inversion scheme where both inductve and galvanic (EM) and galvanic (DCIP) are incorporated into the same inversion framework. To validate the HydroGeosITe both in terms of calibraton and reference, three boreholes are expected to be drilled, the frst of which has been completed in December 2023, reaching the depth of 350 m from the surface. Accurate lithological descripton, along with future borehole-logging, is expected as well, likely positoning the HydroGeosITe as a key reference point in interpretng the future AEM campaign.